Multilayer polymeric optical films are widely used for various purposes, including as mirrors and polarizers. The films are well suited for use as reflectors and polarizers in compact electronic displays, including as liquid crystal displays (LCDs) placed in mobile telephones, personal data assistants, notebook computers, monitors and televisions.
Although polymeric optical films can have favorable optical and physical properties, one limitation with some such films is that they may show dimensional instability when exposed to fluctuations in temperature—even the temperature fluctuations experienced in normal use. This dimensional instability can result in formation of wrinkles in the film, which may be visible in LCDs as shadows. Such dimensional instability can at times be observed for some types of films when temperatures approach or exceed approximately 85° C. Dimensional instability is also observed when some types of films are cycled to high temperature and high humidity conditions, such as conditions of 60° C. and 70 percent relative humidity.